1. Field of the Invention
The present invention relates to a paper feeder, and more particularly to a paper feeder having a drive mechanism for a shutter for preventing an inappropriate operation of a user when placing a stack of sheets on a sheet placing part.
2. Description of the Related Art
In general, an electro-photographic copying machine or a facsimile machine includes an Automatic Document Feeder (ADF). The ADF feeds a stack of sheeted documents set on a document tray, separates the sheeted documents one sheet at a time and transports each sheet towards a scanner. The ADF includes a pick-up roller that feeds the sheeted documents set on the document tray, a separating unit that separates the fed documents one sheet at a time and supplies each sheet to a sheet transportation path, and a transportation roller that is disposed downstream of the separating unit and transports the document towards the scanner. Between the pick-up roller and the separating unit, a shutter that can open and close the sheet transportation path is provided on the sheet transportation path. The shutter prevents an inappropriate operation of a user when placing a stack of sheeted documents. For example, when the user sets a stack of sheeted documents on a sheet placing table, the shutter prevents a sheeted document from being forced between a separate roller and a friction pad that constitute the separating unit. Moreover, the shutter functions to align a leading edge of the sheeted documents.
The paper feeder having the shutter feeds the sheeted documents stacked on the document tray from an uppermost sheet by the pick-up roller. Further, the pick-up roller is provided rotatable on a tip of a pick-up arm that can be elevated and lowered vertically (with a fulcrum as the center). The shutter is controlled to be lowered in response to the elevating and lowering motion of the pick-up roller and to recede below the sheet transportation path. After feeding all of the documents set on the document tray, the shutter protrudes onto the sheet transportation path, and aligns and positions a leading edge of a next sheet. As a mechanism that opens and closes the shutter between a sheet restricting position (a position protruding onto the sheet transportation path) and a non-restricting position (a position receded from the sheet transportation path) and fixes the shutter at each of the positions, a solenoid mechanism having a plunger and an electromagnetic coil is adopted.
The above-described moving mechanism of the shutter is formed of electrical components such as a solenoid. As a result, a number of components increases, and it is necessary to establish a complicated control sequence for synchronizing the moving mechanism of the shutter with another mechanism such as the pick-up roller. The cost of the components and the cost for designing and manufacturing are expensive. In addition, since it is necessary to secure a space for providing the mechanism including the solenoid or the like, it is difficult to downsize the device.